Flame control apparatus



April 22, 1952 w, NAGEL 2,594,059

FLAME CONTROL APPARATUS Filed Dec. 19, 1947 WITNESSES: lNVENTOR W GeorgeM/l/agel 54- I 7M4 I @QM ATTORNEY Patented Apr. 22, 1952 UNITED STATESPATENT OFFICE FLAME CONTROL APPARATUS George W. Nagel, Pittsburgh, Pa",assignor vto Westinghouse.Electric Corporation, EastlPittsburgh, Pa.,.acorporation of Pennsylvania Application December 19, 1947, SerialiNo.792,743

.6 Claims. 1 My invention relates to electric dischargeapparatus and hasparticular relationship 'to apparatus for controlling fuel burners.

Patent 1,809,280 to D. D. Knowles'is illustrative of the prior art ofwhich I am aware-on fuel burner control apparatus. The system shown .inFigure 1 of the Knowles patent includes .a grid glow tube having ablocking electrode. This electrode is connected to a flame probe;another fiameprobe is connected to-the anode. of the tube. The supplysource is connected directly'tothe anode and through the exciting coilof the fuel valve relay to the cathode. the Knowles device, the gridbecomes negative in In the operation of the absence of a flamebetweentheprobes and maintains the tube non-conductive. When a flame isignited between the probes, the negative charge on the grid leaks 01fthrough the flame and the tube becomes conductive.

The system shown in Figure l of the Knowles patent-has not provedentirely'satisfactory. For the proper operation of the grid glow tube,it is essential that the gas in the tube be maintained at apredetermined critical pressure. -If .the

clean-up action of the-discharge in thetubeis I sufficient to reducethe-pressure below the critical magnitude, the grid fails .to functioneffectively and the-tube becomes conductive even in the absence'of-aflame. A dangerouscondition may thus be established by reason'ofunstable operation of the tube.

The Knowles Figurel system is also relatively costly. For properoperation of the tube,-the anode cathode voltage which must be impressedacross the tube should be of the order of 440 volts. Since the poweravailable at the utility receptacles isof the order of 115 volts .inmost localities, a transformer must beinterposed between the commercialpower buses and thetube. The cost-of such items as this transformer soraises the price at which systems such as that disclosed inKnowles-Figurel may be made available as to render such system expensive.-for.-in-

dustrial use and ;prohibitory for use in-homes.

The difficulties arising from instability of operation of the grid glowtube areavoided in a system such as is shown in Figure 2 of the Knowlespatent. The systems showninthis view include a thermionic tube in lieu'of agrid glow tube. A thermionic tube, however, requires facilities forheating .the cathode,-suchas arfilament transformer. This itemand-others-like it incident to the use of a thermionic tubeincreases thecost ofa fuelburner .control system rendering its use in thehome-prohibitive.

.button.

.long-timeinter-vals during-which the system is in operation. Thecathode heating time delay is, however, a severe disadvantage in fuelburners which operate intermittently for. short time-intervals and areturned'on-and-off repeatedly. Such fuel burners are encountered inclothes dryers. Whenraclothes dryeris to be put into operation, thehousewife inserts the clothes in the tank, plugs the power supplyconductor into a receptacleand closes. apushbutton. She expects thatimmediately on the-closing of this push button, the fuel burner systemwill operate and she ,permits the button to open a secondor two aftershe .closes it. If'e, delay of 20 seconds to a minute is involvedin the.cathode heating time, the system will fail to operate on the .reopeningof the The housewife will then continue to open and reclose the pushbutton repeatedly and ,on .finding that the burner fails to operate con-:tinuously,-wil1 phone fora service man. -Adequate printed instructionswill not ameliorate this situation.

Itis, accordingly, an object of my invention to provideastable-low costcontrol for a fuelburner particularly for use in'the home.

.Another-objectof .my invention is to provide a fuel burnercontrol-system which shall operate instantaneously on the closure of.itspower supply circuit.

A further object of my invention is to provide a'fuel-burner controlsystem the componentsaof which shall perform their functions whensubject to; potentials directly available .at receptaclessubpliedfromapublic utility .power station.

.An ancillary objectofmy invention is to provide .a novel circuit .for.an electric discharge device of the ignition electrode type.

=An incidental object of my inventionxis to provide a fuel burnercontrol system particularly suitable for useina clothes-dryer'orsimilar. appliance which is :operated intermittently.

-.-Ano.ther incidentalobject of .my invention is to provide a fuelburner system in the operation of which the fuel shall be shut oif onthe failure of any of the components which are likely to fail.

In accordance with my invention, I provide a fuel burner control systemincluding an electric discharge device of the cold-cathodeignitionelectrode type. Such a device includes a pair of cold mainelectrodes and a firing electrode disposed adjacent to one of the mainelectrodes. To render the discharge device conductive, an auxiliarydischarge is initiated between the firing electrode and its adjacentmain electrode. The ionization produced by the auxiliary dischargecauses a discharge to be produced between-the main electrodes. Apotential of the order of fifty volts between the firing electrode andto adjacent electrodes is sufficient to fire the auxiliary discharge.With this discharge present, a potential of the order of one hundredvolts between the main electrodes is sufiicient to fire the maindischarge.

In accordance with my invention, flame probes are so connected betweenthe firing electrode and the other electrodes of the dischar'g devicethat in the absence of a flame the discharge device is non-conductive.When a flame is burning, a potential is impressedbetween the firingelectrode and its adjacent main electrode and the auxiliary discharge isfired. The resulting firing of the main discharge causes the valvecontrolling the flowof fuel to the burner'to be held open to permit thecontinuous flow of fuel.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following description of a specificembodiment when read in connection with the accompanying drawing, inwhich:

Figure 1 is a view in vertical section showing a clothes dryer includinga fuel burner control system in accordance with my invention;

Fig. 2 is a view in section taken along line I I-.-II of Figure 1;

V 3 is a circuit diagram of a fuel burner control system in accordancewith my invention, and

Fig. 4 is an electric discharge device of the type used in'a fuel burnersystem in accordance with my invention.

The apparatus shown in Figures 1 and 2 comprises a container 5 in whicha clothes tank 1 is mounted rotatable. The tank 1 .is mounted at anangle to the vertical walls of-the container and is provided with a neck9 which extends through an opening H in a slanting portion of the top ofthe container. This opening is covered by a' door which may be pivotedto the open position. Clothes may be inserted in the tank I afteropening the door.

The tank is rotated from an electric motor H and as it is rotated, warmair flows over a portion of its surface and in certain dryers circulateswithin the tank 1. r This air is derived from a flue I9 in the lowerregion of the container 5. Near one end of the flue, a fan 2! drivenfrom the motor I! rotates. The fan draws air from an opening 23 in oneside of the flue and passes the air around a gas flame 25. The gasforthe flame is derived "from a conductor 27 provided withasuitablevalve 295 The operation of the valve is controlled from a flamecontrol unit 3 i.

The flame control unit 3| is shown diagrammatically in Fig. 3. The unitincludes a gaseous electric discharge device 33 of the cold-cathode typehaving an anode 35, a cathode 37 and a firing electrode 39 disposedadjacent to the oathode. The dryer is provided with power supply cable4| terminated by a jack c2. When the jack is plugged into a receptacle(not shown) of a commercial alternating current supply source (notshown), the cathode 31 is connected to one terminal 45 of the powersupply through a resistor 48 and the anode 35 is connected to the otherterminal 49 through the exciting coil 5! of a relay. To prevent therelay from chattering as the alternating current supplied varies, acapacitor 53 of substantial magnitude is connected across the excitingcoil 5!. The current-limiting resistor 48 protects the tube 33. Thefiring electrode 39 is connected to the terminal i"! to which thecathode is connected through a resistor 55. The latter resistor shouldpreferably be of a magnitude of the order of the ionization resistanceof a flame.

The unit 3: is provided, in effect, with two flame probes. One of theflame probes is an ordinary plate 57 preferably composed of stainlesssteel. This probe is connected directly to the firing electrode 39. Theother flame probe may be a ground conductor of the burner, but in thepreferred practice of my invention, is a part of the ignition assembly59 of the burner.

The ignition assembly comprises a U-shaped metallic bar Bl secured to arefractory insulating plate 63 of the dryer and a, rod 65, which passesthrough the plate 83 slidably, and is secured to a magnetic plunger 61.The plunger 61 and rod 55 are urged into engagement with the cross pieceof the U-plate 6| under the action of a spring 69. The U-plate isconnected to the terminal 49 of the supply to which the relay coil 5| isconnected. The rod 55 is adapted to be connected to the other terminal41 of the supply through a solenoid H and a pair of contacts 13 of anormally open starting push button 15. The gas valve solenoid l1 and apilot lamp 19 are adapted to be connected in parallel across theterminals 41 and 49 through the other normally open contacts 8| of thepush button I5.

When the jack 43 is in the receptacle,'the potential of the supply line,usually approximately 115 volts, is impressed between the anode 35 andthe cathode 3! of the discharge device 33. So long as there is no flame25 in the burner, the impedance between the probes 51 and 6! is highcompared to the impedance '55. The potential of the supply line istherefore impressed between the U-plate BI and the other flame probe 51and the potential between the firing electrode 39 and the cathode 3'! islow. The discharge device 33 is non-conductive.

When the housewife closes the push button, the pilot light 19 isenergized and the gas valve is momentarily opened by the closure of oneset of contacts Bl of the button. Gas flows through the burner opening.By the closure of the other set of contacts 1 3 of the button, the rod65 is vibrated out of and into engagement with the U-bar 6| in the samemanner as the hammer of a door bell. The contact connected to the rod 65makes and breaks engagement with the fixed contact 82 connected to coilI I, causing the vibratory motion. The resulting spark which occurs atthe junction of the rod 65 and U-bar Bl ignites the gas and a flame 25burns in the region of the flame probes 51 and BI. A substantialfraction, equal to approximately half, of the source potential is nowimpressed between the firing electrode 39 and the cathode 31. Thispotential is, for the 115 volt 60 cycle supply ordinarily available, ofthe order of 50 volts R. M. S. and is sufficient to produce a dischargebetween the firing electrode and the cathode at an instant in the halfperiod of the source when the source potential is near its maximum. Apotential derived from the source which is approximately equal to itsmaximum potential; that is, of the order of 100 volts R. M. S., is atthe same instant impressed between the main electrodes 35 and 31 of thedischarge device 33. Once the auxiliary discharge is initiated betweenthe firing electrode 39 and the cathode 31 this potential, of the orderof 100 volts R. M. S., is suflicient to initiate the discharge betweenthe main electrodes 3'5 and 3?. The discharge device 33 is conductiveduring each half period of the supply during which the anode 35 ispositive relative to the cathode 31. During the intervening negativehalf periods, it is non-conductive. However, so long as the probes 5'!and BI are under the influence of a flame, the auxiliary discharge willbe reignited during each positive half cycle of the supply potential andthe main discharge is reinitiated following the ignition of theauxiliary discharge.

The current flow through the discharge device 33 causes the relay (5|)to be actuated. During the intervals during which the anode-cathodepotential of the discharge device is negative and the latter isnon-conductive, the exciting coil 5| of the relay is maintainedenergized and the relay maintained actuated by discharge current derivedfrom the capacitor 53 connected in parallel with the coil. The normallyopen contacts 83 of the relay are closed, thus closing a circuit throughthe valve solenoid I1. They also close a circuit in parallel with thevalve solenoid through the pilot lamp 19. The valve solenoid is nowmaintained energized and valve 29 remains open as long as the flamecontinues to burn. If the flame is extinguished for example by a gust ofwind, the firing of the auxiliary discharge during each positive periodof the supply is discontinued, the discharge device 33 is renderednonconductive, the relay (5!) opens and the gas valve 29 closes blockingfurther flow of gas. Because the discharge device functionsinstantaneously and the relay and solenoid are quick acting, the gasflow is discontinued substantially instantaneously and any possibilityof explosion is eliminated. False closing of the valve 29 by reason offlame flicker is precluded by the operation of capacitor 53 in delayingthe opening of the relay (5|). The delay introduced by the networkincluding the relay coil 5| and the condenser 53 is of the order of 1second. During this second the valve 29 does not close even if the flameis extinguished. However, the gas flow during this short interval isinappreciable. This delay may be reduced where the gas flow is at a highrate by reducing the magnitude of the capacitor 53.

The connection of the relay coil 5! and its shunt condenser in theconductor between the power supply line 49 and the anode 35 of thedischarge device is an important feature. When current flows through thedischarge device, the shunt condenser 53 is charged. If this condenserwere connected in the power supply bus 4'! between the terminal of thesupply and the conductor to the anode of the discharge device, thefiring potential available for igniting the auxiliary discharge afterthe discharge device 33 had conducted'during one or a few half periodswould be reduced by the potential impressed on the condenser. Under suchcircumstances an auxiliary discharge frequently would not be ignited andthe discharge device would fail to become conductive, the valve 29 wouldclose and the burner would be turned off. The same condition would beproduced if the relay coil 5! and its shunting condenser 53 wereconnected between the cathode 31 of the discharge device and theterminal 49 of the supply to which it is connected.

In the event of failure of any of the components of the system which arelikely to fail, the gas Valve 29 closes or remains closed. The gas valve29 is closed unless the valve solenoid 11 is energized. If an opencircuit occurs in the valve solenoid or its conductors or if thesolenoid is burned out, the valve remains closed. The solenoid 77remains deenergized unless the relay (5|) is energized by current flowthrough its coil 5!. Should the relay coil or it conductors be opencircuited or should the coil be burned out, the relay will remaindeenergized and the valve 29 will remain closed. If the discharge device33 should fail, current will not flow through the relay coil 5!, therelay will remain unactuated and the gas valve 29 will remain closed.Should the flame probes become short-circuited by a relatively lowresistance suchas soot, for example, the drop produced by the sourcepotential across the flame probles 51 and GI will be small, and thepotential between the anode 35 and firing electrode39 will be too smallto effect transfer of the auxiliary discharge to the anode 35.

I have constructed and successfully tested a flame control system of thetype described herein. In the system tested, the components have thefollowing properties:

Power supplycommercial 114. volts A. C.

cycle My flame control system may be sold at a price within the reach ofthe vast majority of people desiring such control for their homes.

While my invention has been shown herein as included in a clothes dryer,it may be included in a fuel burner system of any type. My invention isparticularly suitable for domestic fuel burners of low B. t. u.capacity.

My invention i shown herein in its specific aspects as controlling thefuel supply to a gas burner. It may be utilized to control the fuelsupply to an oil burner or even a coal burner. In the latter situation,the coal stoker rather than the fuel valve is controlled. Soft coal andoil flames deposit carbon to a greater extent than gas flames. However,no difliculty is to be anticipated from the carbon deposit, because inthe event that it is excessive, the discharge device will fail toconduct and the fuel valve will be maintained closed until theelectrodes are cleaned or the carbon is burned away.

Certain advantages are pointed out above as residing in the specificstructure and arrangement of the components included in my systemasshown herein. However, other components and other arrangements may fallwithin the scope of 7 the broader aspects of my invention. For ex ample,the resistors 48 and 55 may be replaced by impedances of other types.The relay coil may also be connected in the power supply conductor 41rather than in the conductor between the anode of the device and powersupply in situations in which the serious disadvantages inherent in thisconnection are counteracted by other advantages.

While I have shown and described a certain specific embodiment of myinvention, I am fully aware that many modifications thereof arepossible. My invention, therefore, is not to be restricted exceptinsofar as is necessitated by the appended claims.

I claim as my invention:

1. In combination an electric discharge device having a gaseous mediumat a low pressure, at least a first main electrode, a firing electrodeadjacent to said first electrode and a second main electrode, saidfiring electrode and first main electrode beingso spaced and dimensionedthat said device is adapted to have an auxiliary discharge initiatedbetween said firing electrode and said first electrode to produce adischarge between said main electrodes; first and second voltageterminals for supplying a potential to said discharge device; aconnection between said first electrode and said first terminal; circuitmeans including a load between said second terminal and said secondelectrode; a fixed impedance between said firing electrode and saidfirst terminal; a first probe connected to said second terminal, asecond probe connected to said firing electrode;

said probes being normally insulated from each other but in operationhaving a conductive path established therebetween; said fixed impedancebeing so selected that an auxiliary discharge is initiated between saidfiring electrode over said first electrode only if said conductive pathis established.

2. In combination an electric discharge device having a gaseous mediumat a low pressure, at least a first main electrode, a firing electrodeadjacent to said first electrode and a second main electrode, saidfiring electrode and first main electrode being so spaced anddimensioned that said device is adapted to have an auxiliary dischargeinitiated between said firing electrode and said first electrode toproduce a discharge between said main electrodes; said auxiliarydischarge being initiated if a potential of the order of volts R. M. S.is impressed between said firing electrode and said first electrode andsaid discharge between said main electrodes being initiated in thepresence of an auxiliary discharge if a potential of the order of 100volts R. M. S. is impressed between said main electrodes; first andsecond voltage terminals for supplying a potential to said dischargedevice; a connection between said first electrode and said firstterminals; a connection including a load between said second terminaland said second electrode;

' a fixed impedance between said firing electrode and said firstterminal and a variable impedance between said firing electrode and saidsecond terminal; said fixed impedance being so selected that anauxiliary discharge is initiated between said firing electrode over saidfirst electrode only if said variable impedance is less than apredetermined magnitude.

3. Apparatus for controlling the operation of a fuel burner including aconduit for supplying fuel to be burned and a mechanism operable whenclosed to block. or when open, to permit the flow of fuel through saidconduit; comprising in combination an electric discharge device having agaseous medium at a low pressure, at least a first main electrode, afiring electrode adjacent to said first electrode and a second mainelectrode, said firing electrode and first main electrode being sospaced and dimensioned that said device is adapted to have an auxiliarydischarge initiated between said firing electrode and said firstelectrode to produce a discharge between said main electrodes; first andsecond voltage terminals for supplying a potential to said dischargedevice; a connection between said first electrode and said firstterminal; circuit means including a motor between said second terminaland said second electrode; said motor being adapted to maintain saidmechanism open when said current flows; a fixed impedance between said.firing electrode and said first terminal; a first probe connected tosaid second terminal, a second probe connected to said firing electrode;said probes being adapted to be disposed in a flame produced by saidfuel when it is burned; said fixed impedance being so selected that anauxiliary discharge is initiated between said firing electrode over saidfirst electrode only if said conductive path is established.

4. Apparatus for controlling the operation of a fuel burner including aconduit for supplying fuel to be burned and a mechanism operable whenclosed to block, or when open, to permit the fiow of fuel through saidconduit; comprising in combination an electric discharge device having agaseous medium at a low pressure, at least a first main electrode, afiring electrode adjacent to said first electrode and a second mainelectrode, said firing electrode and first main electrode being sospaced and dimensioned that said device is adapted to have an auxiliarydischarge initiated between said firing electrode and said firstelectrode to produce a discharge between said main electrodes; first andsecond voltage terminals for supplying a potential to said dischargedevice; a connection between said first electrode and said firstterminal, said connection including a resistance low compared with theionization resistance of a fiame of said fuel when it is burned; circuitmeans including a motor between said second terminal and said secondelectrode; said motor being actuable by current flow through saidcircuit and adapted to actuate said mechanism; a fixed impedance betweensaid firing electrode and said first terminal; said fixed impedancehaving a resistance of the order of magnitude of the ionizationresistance of said flame; a first probe connected to said secondterminal, a second probe connected to said firing electrode; said probesbeing adapted to be'disposed in the flame produced by said fuel when itis burned; said fixed impedance being so selected that an auxiliarydischarge is initiated between said firing electrode over said firstelectrode only'if said conductive path is established.

5. Apparatus for controlling the operation of a fuel burner including aconduit for supplying fuel to be burned and a mechanism operable whenclosed to block, or when open, to permit the flow of fuel through saidconduit; comprising in combination an electric discharge device having agaseous medium at a low pressure, at least a first main electrode, afiring electrode adjacent to said first electrode and a second mainelectrode, said firing electrode and first main electrode being sospaced and dimensioned that said device is adapted to have an auxiliarydischarge ini- 9 tiated between said firing electrode and said firstelectrode to produce a discharge between said main electrodes; saidauxiliary discharge being initiated if a potential of the order of 50volts R. M. S. is impressed between said filing electrode and said firstelectrode and said discharge between said main electrodes beinginitiated in the presence of an auxiliary discharge if a potential ofthe order of 100 volts R. M. S. is impressed between said mainelectrodes; first and second voltage terminals for supplying a potentialto said discharge device; a connection between said first electrode andsaid first terminals; a connection including a motor responsive to theresultant current flow between said main electrodes adapted to maintainsaid mechanism open when said current flows, said motor being connectedbetween said second terminal and said second electrode; a fixedimpedance between said firing electrode and said first terminal and avariable impedance between said firing electrode and said secondterminal; said fixed impedance being so selected that an auxiliarydischarge is initiated between said firing electrode over said firstelectrode only if said variable impedance is less than a predeterminedmagnitude.

6. Apparatus for controlling the operation of a fuel burner including aconduit for supplying fuel to be burned and a mechanism operable whenclosed to block, or when open, to permit the flow of fuel through saidconduit; comprising in combination an electric discharge device having agaseous medium at a low pressure, at least a first main electrode, afiring electrode adjacent to said first electrode and a second mainelectrode, said firing electrode and first main electrode being sospaced and dimensioned that said device is adapted to have an auxiliarydischarge initiated between said firing electrode and said firstelectrode to produce a discharge between said main electrodes; saidauxiliary discharge being initiated if a potential of the order of 50volts R. M. S. is impressed between said firing electrode and said firstelectrode and said discharge between said main electrodes beinginitiated in 10 the presence of an auxiliary discharge if a potential ofthe order of volts R. M. S. is impressed between said main electrodes;first and second voltage terminals for supplying a potential to saiddischarge device; a connection between said first electrode and saidfirst terminals; said connection including a first resistance lowcompared with the ionization resistance of the flame of said fuel whenit is burned; a connection including a motor actuable by current flowthrough a conductor thereof and adapted to actuate said mechanism, saidmotor being connected between said second terminal and said secondelectrode; a capacitor connected in parallel with said motor, a fixedimpedance having a resistance of the order of magnitude of theionization resistance of a fiame of said fuel when it is burned betweensaid firing electrode and said first terminal and a pair of fiameelectrodes adapted to be disposed in a flame of said fuel when it isburned, said firing electrodes being connected through said ionizationpath to said second terminal; said fixed impedance being so selectedthat an auxiliary discharge is initiated between said firing electrodeover said first electrode only if said variable impedance is less than apredetermined magnitude.

GEORGE W. NAGEL.

REFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS

